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[Aethelric]

It is difficult to know what will happen with both the powerbox and the zener diode in the circuit. For example if one is at the bottom end of it’s tolerance (say 14V) and the other is at the top end (say 15V) then the higher one will never contribute.

A zener diode has to dissipate much more power then a rec/reg. A zener working alone will have to get rid of most of the total output of the alternator - 100-200W.

A rec/reg works by shorting the alternator out before the rectifier so most the power is dissipated in the alternator.

So if your zener still gets hot it’s doing it’s job. If not then it’s on standby until the powerbox fails. (you probably won’t notice depending on how it fails - short circuit or open circuit). If the zener does not have sufficient cooling it will fail very quickly.

The number plate MAY be ok as a heatsink but I doubt that it will be thick enough to conduct the heat away.

[Beezabryan]

Don't know if my addled old head is reading this correctly or confusedly. Using zener and powerbox together is a bad idea, one or t'other but not both.

[Adrian]

Gentlemen,



you don't appear to have read Davedup's follow-up posts to this thread properly. He has not been using a Power Box AND a separate rectifier/zener together, he realised he had merely mistaken the ignition's TCI box for a Power Box. I suppose it's an easy mistake, they're both black boxes with wires coming out and both made by Boyer Bransden.



Where an actual Power Box does now come into the story is as a REPLACEMENT for the zener and separate rectifier. So the Davedup's Super Meteor now has/is getting a Boyer Power Box (originally intended for a different bike) as the sole means of rectifying and regulating the alternator output, as well as the Boyer TCI box already fitted to control the electronic ignition.



It's too hot for all this...



A.

[Aethelric]

Oops, you are right - too hot to take it all in.

Back number plate should be fine for the power box, - but maybe a bit exposed to road dirt as Adrian says.